1. Field of the Invention
The present invention relates to an injection device for a steam iron. This device comprises more particularly a nozzle mounted within an opening in a wall which forms a separation between a water reservoir and a vaporization chamber, said chamber being located beneath the reservoir when the iron is in service. The nozzle has an annular lip which delimits a communication orifice between the reservoir and the chamber. Said nozzle also has a skirt which surrounds the flow passage downstream of the lip with respect to the direction of flow. The device further comprises an injection plunger which is provided with a lateral recess, said plunger being axially displaceable within the orifice between a closed position in which the lip surrounds the plunger between a free end of this latter and the lateral recess, and an injection position in which the lip surrounds the plunger between the two axial ends of said lateral recess.
2. Description of the Prior Art
A known device of this type has already been disclosed in French patent No. FR-A-2,449,157. When the injection plunger moves from one end position to the other, it subjects the lip to flexural deformation and prevents scale formation. Since the smooth region is located beneath the axial recess under operating conditions, the plunger can be moved to the injection position simply by exerting downward pressure, which is a convenient procedure.
This simple construction is nevertheless attended by a disadvantage in that a sheath of scale tends to form beneath the lip around the smooth region of the injection plunger. In such a case, even if the user places the plunger in the injection position, the smooth region of the plunger which is surrounded by and joined to the sheath of scale prevents the water from reaching the vaporization chamber. If the plunger remains in the injection position over a long period of time, it may even be locked in this position as a result of scale formation.
Swiss patent No. CH-A-448,004 discloses an injection device having a nozzle comprising a concave conical seat followed by a calibrated cylindrical orifice at the lower end. A valve which is capable of moving along the axis of the nozzle cooperates with the seat and is adapted to carry in addition a pintle which is engaged within the calibrated orifice when the valve is in the closed position. On the contrary, when the valve is moved away from its seat, the pintle is located above the orifice and the water flows in principle at a rate which is determined by calibration of the orifice. When the valve returns to the closed position, the pintle causes a downward displacement of the scale deposit which may have formed within the orifice and prevents this orifice from subsequently becoming completely incrusted with scale if the device is not actuated for a certain length of time.
In order to overcome the difficulty which may be experienced when operating the valve if the scale forms an adhesive film between the pintle and the orifice, provision is made at the end of the pintle for a spherical bulge or head which is located beyond the orifice when the valve is closed. When the user again opens the valve, the pintle-head is intended to sweep the orifice and thus to produce a de-scaling action. This expedient, however, is not very effective. In point of fact, if the scale has the effect of subjecting the pintle to a braking action, it is difficult if not actually impossible to engage the head within the orifice. Furthermore, if the pintle is jammed within the orifice instead of being simply braked, the pintle-head which is located beyond the orifice cannot produce any action. Supposing finally that the pintle-head performs its function and causes the scale to move upwards to the region of the valve-seat, then either the scale will subsequently impair the leak-tightness of the valve in the closed position or else it will fall back into the orifice and will immediately re-incrust this latter.